Workaround lack of timeout on Py2

Author: takluyver

jupyter_client/tests/test_kernelapp.py

@@ -7,16 +7,28 @@
 from tempfile import mkdtemp
 import time
 
+PY3 = sys.version_info[0] >= 3
+
 def _launch(extra_env):
     env = os.environ.copy()
     env.update(extra_env)
     return Popen([sys.executable, '-c',
                   'from jupyter_client.kernelapp import main; main()'],
-                 env=env, stderr=PIPE)
+                 env=env, stderr=(PIPE if PY3 else None))
 
 WAIT_TIME = 10
 POLL_FREQ = 10
 
+def hacky_wait(p):
+    """Python 2 subprocess doesn't have timeouts :-("""
+    for _ in range(WAIT_TIME * POLL_FREQ):
+        if p.poll() is not None:
+            return p.returncode
+        time.sleep(1 / POLL_FREQ)
+    else:
+        raise AssertionError("Process didn't exit in {} seconds"
+                             .format(WAIT_TIME))
+
 def test_kernelapp_lifecycle():
     # Check that 'jupyter kernel' starts and terminates OK.
     runtime_dir = mkdtemp()
@@ -42,15 +54,13 @@ def test_kernelapp_lifecycle():
         assert cf.startswith('kernel')
         assert cf.endswith('.json')
 
-        # Read the first three lines from stderr. This will hang if there are
-        # fewer lines to read; I don't see any way to avoid that without lots
-        # of extra complexity.
-        b = b''.join(p.stderr.readline() for _ in range(2)).decode('utf-8', 'replace')
-        assert cf in b
-
         # Send SIGTERM to shut down
         p.terminate()
-        p.wait(timeout=10)
+        if PY3:
+            _, stderr = p.communicate(timeout=WAIT_TIME)
+            assert cf in stderr.decode('utf-8', 'replace')
+        else:
+            hacky_wait(p)
     finally:
         shutil.rmtree(runtime_dir)
         shutil.rmtree(startup_dir)